* My last change to vm_page.cpp made an existing bug much more likely to

appear: when freeing a modified page, it wouldn't have a cache
  anymore, but set_page_state_nolock() depended on it.
* To work around this, I added a vm_page_free() function, which the
  caches that free modified pages have to call (but others may, too).
  It will correctly maintain the sModifiedTemporaryPages counter in case
  the cache has already been removed.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@23318 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/vm_page.h

@@ -26,6 +26,7 @@ status_t vm_page_init_post_thread(struct kernel_args *args);
 
 status_t vm_mark_page_inuse(addr_t page);
 status_t vm_mark_page_range_inuse(addr_t startPage, addr_t length);
+void vm_page_free(struct vm_cache *cache, struct vm_page *page);
 status_t vm_page_set_state(struct vm_page *page, int state);
 void vm_page_requeue(struct vm_page *page, bool tail);
 

src/system/kernel/vm/vm_cache.cpp

@@ -152,7 +152,7 @@ delete_cache(vm_cache *cache)
 
 		TRACE(("vm_cache_release_ref: freeing page 0x%lx\n",
 			oldPage->physical_page_number));
-		vm_page_set_state(oldPage, PAGE_STATE_FREE);
+		vm_page_free(cache, oldPage);
 	}
 
 	// remove the ref to the source
@@ -514,7 +514,7 @@ vm_cache_resize(vm_cache *cache, off_t newSize)
 
 				// remove the page and put it into the free queue
 				vm_cache_remove_page(cache, page);
-				vm_page_set_state(page, PAGE_STATE_FREE);
+				vm_page_free(cache, page);
 			}
 
 			page = next;

src/system/kernel/vm/vm_page.cpp

@@ -656,17 +656,20 @@ set_page_state_nolock(vm_page *page, int pageState)
 			panic("vm_page_set_state: invalid target state %d\n", pageState);
 	}
 
-	if (pageState == PAGE_STATE_CLEAR || pageState == PAGE_STATE_FREE || pageState == PAGE_STATE_INACTIVE) {
+	if (pageState == PAGE_STATE_CLEAR || pageState == PAGE_STATE_FREE
+		|| pageState == PAGE_STATE_INACTIVE) {
 		if (sPageDeficit > 0)
 			sFreePageCondition.NotifyOne();
 
 		if (pageState != PAGE_STATE_INACTIVE && page->cache != NULL)
 			panic("to be freed page %p has cache", page);
 	}
-	if (pageState == PAGE_STATE_MODIFIED && page->cache->temporary)
+	if (page->cache != NULL) {
-		sModifiedTemporaryPages++;
+		if (pageState == PAGE_STATE_MODIFIED && page->cache->temporary)
-	else if (page->state == PAGE_STATE_MODIFIED && page->cache->temporary)
+			sModifiedTemporaryPages++;
-		sModifiedTemporaryPages--;
+		else if (page->state == PAGE_STATE_MODIFIED && page->cache->temporary)
+			sModifiedTemporaryPages--;
+	}
 
 #if TRACK_PAGE_ALLOCATIONS
 	if ((pageState == PAGE_STATE_CLEAR || pageState == PAGE_STATE_FREE)
@@ -1708,6 +1711,23 @@ vm_lookup_page(addr_t pageNumber)
 }
 
 
+/*!	Free the page that belonged to a certain cache.
+	You can use vm_page_set_state() manually if you prefer, but only
+	if the page does not equal PAGE_STATE_MODIFIED.
+*/
+void
+vm_page_free(vm_cache *cache, vm_page *page)
+{
+	InterruptsSpinLocker _(sPageLock);
+
+	if (page->cache == NULL && page->state == PAGE_STATE_MODIFIED
+		&& cache->temporary)
+		sModifiedTemporaryPages--;
+
+	set_page_state_nolock(page, PAGE_STATE_FREE);
+}
+
+
 status_t
 vm_page_set_state(vm_page *page, int pageState)
 {